Handle urwid API deprecations

* `_set_original_widget` -> `original_widget` property (setter)
* `button._state` -> `button.get_state()`
  (not deprecated, but we have public getter)

toot/tui/timeline.py

@@ -338,9 +338,9 @@ def update_status_image(self, status, path, placeholder_index):
                 pass
         if img:
             try:
-                status.placeholders[placeholder_index]._set_original_widget(
-                    graphics_widget(img, image_format=self.tui.options.image_format, corner_radius=10,
-                                    colors=self.tui.options.colors))
+                status.placeholders[placeholder_index].original_widget = graphics_widget(
+                    img, image_format=self.tui.options.image_format, corner_radius=10, colors=self.tui.options.colors
+                )
 
             except IndexError:
                 # ignore IndexErrors.

toot/tui/widgets.py

@@ -58,7 +58,7 @@ def __init__(self, *args, **kwargs):
 
     def get_state(self):
         """Return the state of the checkbox."""
-        return self.button._state
+        return self.button.get_state()
 
 
 class RadioButton(urwid.AttrWrap):